<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
	</body>
	<script>
		//向上向下取整 地板  天花板
		var num =Math.floor(8.9)
		var num2 =Math.ceil(8.9)
		console.log(num)
		console.log(num2)
	</script>
</html>
